September weather forecastMill Valley, CA
September
Weather in September
The first month of the autumn, September, is still a pleasant month in Mill Valley, California, with an average temperature varying between 56.1°F (13.4°C) and 72.3°F (22.4°C).Temperature
Temperature readings reach their annual highs in September, averaging 72.3°F (22.4°C) and a minimum average of 56.1°F (13.4°C).Humidity
In September, the average relative humidity is 71%.Rainfall
June through September are months with the least rain in Mill Valley when the rain falls for 1.7 days and typically aggregates up to 0.04" (1mm) of rain.Daylight
The average length of the day in September is 12h and 25min.On the first day of September, sunrise is at 6:40 am and sunset at 7:38 pm. On the last day of the month, sunrise is at 7:05 am and sunset at 6:54 pm PDT.
Sunshine
The average sunshine in September is 10.4h.UV index
The months with the highest UV index are April, June through September, with an average maximum UV index of 5. A UV Index value of 3 to 5 symbolizes a medium vulnerability from unsafe exposure to UV radiation for the ordinary person.Note: In September, an average UV index of 5 transforms into the following instructions:
Act with care - The suggestion to avoid sunburn is emphasized. Being exposed to the midday Sun can have harmful effects due to strong UV radiation; always take precautions. Employ a hat with a wide brim for robust protection, cutting UV exposure by half.
Published by: Weather U.S. | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
Average temperature in September
Mill Valley, CA
- Average high temperature in September: 72.3°F
The warmest month (with the highest average high temperature) is September (72.3°F).
The month with the lowest average high temperature is December (55.4°F).
- Average low temperature in September: 56.1°F
The month with the highest average low temperature is September (56.1°F).
The coldest month (with the lowest average low temperature) is December (45.3°F).
Average pressure in September
Mill Valley, CA
- Average pressure in September: 29.92"Hg
The month with the highest atmospheric pressure is January (30.13"Hg).
The months with the lowest atmospheric pressure are June, August and September (29.92"Hg).
Average wind speed in September
Mill Valley, CA
- Average wind speed in September: 5.9mph
The windiest month (with the highest average wind speed) is May (7.8mph).
The calmest months (with the lowest average wind speed) are October and November (5.5mph).
Average humidity in September
Mill Valley, CA
- Average humidity in September: 71%
The month with the highest relative humidity is March (77%).
The month with the lowest relative humidity is October (68%).
Average rainfall in September
Mill Valley, CA
- Average rainfall in September: 0.04"
The wettest month (with the highest rainfall) is February (0.87").
The driest months (with the least rainfall) are June, July, August and September (0.04").
Average rainfall days in September
Mill Valley, CA
- Average rainfall days in September: 1.7 days
The month with the highest number of rainy days is March (8.8 days).
The months with the least rainy days are June and August (1.2 days).
Average daylight in September /
Average sunshine in September
Mill Valley, CA
- Average daylight in September: 12h and 24min
The month with the longest days is June (Average daylight: 14h and 48min).
The month with the shortest days is December (Average daylight: 9h and 36min).
- Average sunshine in September: 10h and 24min
The month with the most sunshine is July (Average sunshine: 11h and 12min).
The month with the least sunshine is December (Average sunshine: 5h and 30min).
Average sunshine days in September
Mill Valley, CA
- Average sunshine days in September: 26 days
The month with the most sunshine days is June (26.4 days).
The month with the least sunshine days is March (20.7 days).
Average UV index in September
Mill Valley, CA
- Average UV index in September: 5
The months with the highest UV index are April, June, July, August and September (UV index 5).
The months with the lowest UV index are January, February, November and December (UV index 3).
Average cloud cover in September
Mill Valley, CA
- Average cloud cover in September: 19
The month with the most cloud cover is March (Cloud cover 39).
The month with the least cloud cover is September (Cloud cover 19).
Average visibility in September
Mill Valley, CA
- Average visibility in September: 6mi
The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
